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Epilithic diatom community of Tolmia Stream, as well as physicochemical properties of the stream were studied through samples collected from the specified 4 stations in monthly periods for one year. 70 species from 21 genera were identified in the study. In epilithon in the stations. Navicula spp. (16 taxa) was the most remarkable genus in terms of both number of species and the number of individuals from species and this was followed by Cymbella (13 taxa) and Nitzschia (9 taxa). The water quality in the Tolmia stream varied at different stations based on levels of pollution. The epilithic diatom communities responded to changes in the aquatic environment. Dominant species had variation among the stations. Dominant species of the station 1 were Cocconeis placentula, Diatoma vulgaris, Cymbella afflnis and Gomphonema olivaceum. Navicula eiyptocephala, C. minuta, Ulnana ulna, Nitzschia amphibia, and N thermalis were dominant diatoms of the stations 2 and 3. Dominant diatoms of the station 4 were Achnanthidium minutissimum, N palea, Gomphonema pairulum, and Surirella an gust at a. diversity of diatoms also varied in all stations in parallel to water quality. Also, station 4 in Beyler Brook in which wastes of 1st and 2nd Organized industry zones are discharged joins to Tolmia stream. We concluded that Tolmia stream has a water quality gradient and this led to apparent variances in species composition of diatom across the stream. The results have confirmed that epilithic diatoms are crucial biological indicators to evaluate ecological quality of Tolmia stream. [ABSTRACT FROM AUTHOR]

Epilithic diatoms were examined longitudinally with respect to trophic status and factor governing their distribution from a spring-fed lesser Himalayan stream; the Khanda Gad. The samples were collected at 4 stations from headwater to mouth; K1 to K4. The annual means of environmental variables - water temperature, channel width, depth, current velocity, discharge and dissolved oxygen increased from ?1 to K4 downstream. The taxa were grouped into exceptionally high (>50%), moderate (20-50%) and low (10-20%) abundance. The species, Achnanthidium minutissimum, Cymbella affinis, Cocconeis placentula var. euglypta and Gomphonema olivaceumwere abundant longitudinally. The longitudinal variation in the taxa abundance downstream were; decreasing abundance (Achnanthidium minutissimum, Planothidiumfrequentissimum, Platessa conspicua), increasing abundance {Cymbella affinis1 Cocconeis placentula var. euglypta, G. olivaceum) and other abundant taxa that appeared and disappeared. The trophic state was eutraphentic at ?1 and K4, while mesoeutraphentic at K2 and ??. The share of eutraphentic and mesoeutraphentic taxa varied little at ?1 but was considerably different at K4 compared to K2 and ?? where both forms accounted for 24-25% each. [ABSTRACT FROM AUTHOR]

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Abstract: We report biological changes at several UK Acid Waters Monitoring Network lakes and streams that are spatially consistent with the recovery of water chemistry induced by reductions in acid deposition. These include trends toward more acid-sensitive epilithic diatom and macroinvertebrate assemblages, an increasing proportional abundance of macroinvertebrate predators, an increasing occurrence of acid-sensitive aquatic macrophyte species, and the recent appearance of juvenile (<1 year old) brown trout in some of the more acidic flowing waters. Changes are often shown to be directly linked to annual variations in acidity. Although indicative of biological improvement in response to improving water chemistry, “recovery” in most cases is modest and very gradual. While specific ecological recovery endpoints are uncertain, it is likely that physical and biotic interactions are influencing the rate of recovery of certain groups of organisms at particular sites. [Copyright &y& Elsevier]

Copyright of Brazilian Journal of Biology is the property of Instituto Internacional de Ecologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)